Forest Herbicides for Vegetation Management

Forest Herbicide Prescription Recommendations (NEW)

A new support tool for forest herbicide prescription selection is now available. The
manual describes herbicide prescriptions in light of a specific management context.
The new tool will help forest managers make more informed decisions regarding applications
to forests.

Competing vegetation or competition is always a concern in forest management. Controlling
competition to crop trees (e.g. pine or oak seedlings) in forest management is an
essential management operation that will assist in optimizing production and revenue
from timber management. Many forest researchers believe competition control provides
the most benefit to survival and growth over any silvicultural (forest management)
method available. Specific benefits of competition control include:

Increased nutrient availability to crop trees

Increased water availability

Increased sunlight availability

Increased seedling survival

Increased growth rates

Shorter rotation lengths

Increased revenues

Common Questions Regarding Herbicide Applications

What are the Primary Concerns with Herbicide Applications in Forestry?

Grasses and broadleaf weeds can be serious competitors for planted seedlings.

There are many herbicides available for use in forest management operations. Each
herbicide is designed for specific uses. Several considerations should be made prior
to making an application, including species, site conditions and environment.

Species Concerns:

What are the crop trees?

Pine or hardwood

species requirements -resistance/susceptibility

What are the primary competitors?

Grasses

Broadleaf weeds

Vines

Shrubs

Other tree species

Site Conditions:

Size of area to be treated

Effects method of application, whether a contractor is needed and cost.

Topography

Steep terrain can create difficulty in ground applications.

Structure of vegetation present

Effects equipment used in application.

Soil type

Soil texture and drainage can impact how effective some herbicides will be.

Wildlife habitat

Forestry herbicides usually exhibit low toxicity to animals. Habitat alterations are
most important and they could be positive or negative to wildlife.

Sensitive areas

Endangered species, water sources, crops, and other sensitive areas should be identified
and protected from herbicide applications.

Environment:

Herbicide applications can increase both survival and growth of planted seedlings.

What are the Types of Applications Made in Pine Stands?

Controlling competing vegetation prior to planting is much easier than post planting.
Furthermore, there will be many more application rate options available prior to planting.

Release from hardwood competition

There are two times to release pines from hardwood competition 1. During establishment
(first year or two) and 2. prior to a fertilization treatment at mid-rotation (~15
years in rotation).

Herbaceous weed control

In the first year after seedlings are planted, grasses and broadleaf weeds can effect
survival and growth. Several herbicides are available to spray over the top of pine
trees. Again, these will be lower rates than could have been applied at site preparation.

What are the Types of Applications Made in Hardwood Stands?

Site preparation prior to planting

There are fewer herbicides that can be used on hardwood plantings than in pine. Apply
foliar active only herbicides in late growing season (prior to planting in the following
spring) to control competing vegetation. A couple of soil active herbicides are available
to apply just prior to planting in late winter to early spring. Once hardwood seedlings
break bud in spring, only grass herbicides may be applied.

Herbaceous weed control

Again this is most effectively addressed prior to planting. Grasses may be controlled
by a few grass herbicides after leaf out. Options for competition control during the
growing season are extremely limited with hardwood seedlings

Timber Stand Improvement (TSI)

This operation is typically performed in existing stands to improve species composition
and increase sunlight reaching developing desirable regeneration. TSI is performed
by applying herbicide to individual undesirable stems (Site Preparation for Natural Regeneration of Hardwoods).

What are the Application Methods?

Typically performed on large acreages, steep terrain, or heavy vegetative cover using
a helicopter mounted sprayer.

Broadcast ground applications

These applications are carried out using a skidder, tractor, or four wheeler, depending
on size of area and vegetative structure.

Banded and spot ground applications

Can be performed with a four wheeler for banding and/or backpack/handheld sprayers
for spot spraying.

Directed sprays

Directed sprays are performed with a backpack or handheld sprayer and are sprayed
only on competition. Care is taken to avoid herbicide contact with seedlings.

Aerial, broadcast ground and banded ground applications

Properly planned and implemented herbicide applications can be very useful in forest
management. Improperly planned and/or misapplication can be harmful and costly. Therefore,
taking steps to ensure proper application are essential.